Mine's not a side project, but I think its as interestint. After working on json-dsl for recommendation execution planning and carried that design to our search middleware, now I'm working in a "CQRS+Eventsourcing like" solution with dags-driven extendable state machines that gives a git-like vensioning view of some business entity. The chalenge is to guarantee that it'll work in a very efficient way (cost x latency) and be a good high-level abstraction platform for many product teams to work on in a safe, transparent and productive way. When being locally successfull, as it does not carry any business-specific code, we can plan to make it open-source. Looking forward to share the details with all comunity.